1. Field of the Invention
The present invention relates to a method and an apparatus for automatically exchanging a full cloth roll (i.e. a roll of woven fabric or cloth fully wound) with an empty cloth roll (i.e. a roll having no cloth wound thereon) in a weaving machine installation. The present invention also relates to detection of woven fabric or cloth (hereinafter referred to as the cloth), detection of a tension imparted to the cloth extending between the full cloth roll and the empty cloth roll, and cutting thereof in the cloth roll exchange apparatus.
2. Description of the Prior Art
The automatic cloth roll exchange apparatuses of the type mentioned above are disclosed in Japanese Unexamined Patent Application Publication No. 17956/1985 (JP-A-60-17956), Unexamined Utility Model Application Publication No. 177143/1985 (JU-A-60-177143), Unexamined Patent Application Publication No. 23060/1986 (JP-A-61-23060) and Unexamined Patent Application Publication No. 97241/1989 (JP-A-H1-97241).
The automatic cloth roll exchange apparatus disclosed in JP-A-60-17956 and JU-A-60-177143 is installed on a cloth roll transporting carriage or bogie which is called upon completion of cloth winding on a cloth roll in a weaving machine or loom to move to a cloth roll transfer position located in front of the loom. Upon arrival of the transporting carriage at the cloth roll transfer position, the automatic cloth roll exchange apparatus installed on the carriage performs a series of cloth roll exchange operations, whereby the cloth roll fully wound (hereinafter referred to as the full cloth roll or simply as the full roll) is transferred onto the transporting carriage while an empty cloth roll (hereinafter also referred to simply as the empty roll) carried on the transporting carriage is shifted to the loom. Subsequently, a cloth cutting mechanism constituting a part of the automatic cloth roll exchange apparatus cuts the cloth extending between the empty roll and the full roll. A leading end portion of the cloth as cut is wound around the empty roll, while a trailing end portion of the cloth is wound up around the full roll. The empty roll transferred to the cloth wind-up position in the loom is operatively coupled to a loom driving motor. In that case, the winding of the leading end portion of the cloth onto the empty roll is realized by making use of air jets. The empty roll onto which the leading end portion of cloth has been wound starts to take up the cloth. Thus, the cloth roll exchange can be carried out without need for stopping operation of the loom.
On the other hand, in the case of the exchange apparatuses disclosed in JP-A-60-17956 and JU-A-60-177143, the full roll transferred to the cloth roll transporting carriage is imparted with a tension by rotating the full roll, and the cloth cutting is performed in the tensioned state of the cloth. The weaving operation is continued even during the cloth roll exchange operation. As a consequence, the cloth is cut obliquely, whereby a number of wefts are cut as well, resulting in that the cutting property of the cutter undergoes degradation within a short time. Also, the oblique cutting is likely to involve irregular cut because of significant sliding or frictional resistance exerted to a side surface of the cutting blade.
In the exchange apparatuses disclosed in JP-A-60-17956, JU-A-60-177143 and JP-A-61-23060, a single cloth roll transporting carriage is designed to serve a plurality of weaving machines or looms. Consequently, there may arise such situation that a lot of time is taken for the cloth roll carriage to arrive at the loom requesting the cloth roll exchange. In that case, the length of the woven fabric or cloth will exceed considerably the predetermined length. To avoid such undesirable situation, the loom operation must necessarily be stopped, which apparently results in poor operation efficiency or availability of the loom.
In the prior art apparatus disclosed in JP-A-H1-97241, a full cloth roll disposed at the cloth wind-up position and supported by a pair of driving rollers is pushed outwardly by a push-out lever and rolls out onto a cloth receiving lever which is thereby caused to swing downwardly against a force of a tension spring from the upstanding state. Subsequently, an empty roll is dropped into the cloth wind-up position, where upon the cloth spanning the empty roll and the full roll is cut by a cutter moved in the direction widthwise of the cloth. In this way, the weaving operation can be performed by temporarily placing the full roll on the receiving lever.
However, in the case of the exchange apparatus disclosed in JP-A-H1-97241, the loom operation is temporarily stopped during the cloth roll exchange process. Otherwise, the driving rollers supporting the full cloth roll will feed the cloth pressed against the driving rollers under the gravity of the empty roll placed thereon to the full cloth roll disposed at the temporary storage position on the cloth receiving lever, which results in that the cloth existing between the empty roll and the full roll is slackened, making it impossible to cut the cloth. For this reason, temporary stoppage of the loom operation is unavoidable.
Furthermore, in the automatic cloth roll exchange apparatus disclosed in JP-A-H1-97241, detection of presence of the cloth rolls at the supporting positions, i.e. the cloth wind-up position and the temporary storage position, is indispensably required in order to automatically execute a sequence of operations involved in the cloth roll exchange, i.e., discharge of the full cloth roll from the cloth wind-up position to the temporary storage position, disposition of the empty roll at the cloth wind-up position, and cutting of the cloth extending from the full cloth roll located at the temporary storage position. Also, there are required not only detection of the leading end portion of the cloth wound around the empty roll disposed at the cloth winding position, but also detection of the tension of the cloth in order to ensure a satisfactory cutting thereof.
In this conjunction, there is disclosed in JP-A-H2-52839 a cloth take-up detecting device which includes a disk plate fixedly mounted on a driving shaft operatively coupled to a shaft of the empty roll and a proximity switch adapted to detect a groove/projection repetition row circularly arrayed on the disk plate. The proximity switch generates a pulse signal having a frequency which corresponds to the rotational speed of the disk plate, wherein completion of the operation for winding the leading end portion of the cloth onto the empty roll is determined by detecting a decrease in the frequency of the signal generated by the proximity switch. Rotation of the empty roll for taking up the leading end portion of the cloth is performed by deriving a driving power from a loom driving motor through a transmission system in which a torque limiter is incorporated for maintaining constant the tension applied to the cloth being wound up during the weaving operation. In this conjunction, it is noted that the empty roll having no cloth wound thereon will rotate at a higher speed as compared with the rotational speed thereof during the normal weaving operation. Accordingly, upon completion of operation for winding the leading end portion of the cloth around the empty roll, tension of the cloth will increase up to a predetermined value. Thus, detection of completed operation of winding the leading end portion onto the empty roll can be realized by detecting change in the tension of the cloth.
However, because the disk plate is not mounted on the shaft of the empty roll, there is required an additional detector for detecting presence or absence of the empty roll at the cloth wind-up position. An increase in the number of detectors means a limitation imposed on the design choice of the complicated mechanism of the cloth roll exchange apparatus.
Furthermore, it should be added that JP-A-H1-28554 discloses a cloth roll transfer apparatus in which a temporary full roll storage position is provided on a transfer carriage which can moved between a stand-by position closely located to the cloth wind-up position and a transfer position for transferring the full roll to a cloth roll transporting carriage. However, this prior art cloth roll exchange apparatus includes no mechanism for placing the empty roll at the cloth wind-up position and therefore relies on manual operation for exchanging the full roll with the empty roll.